Bacterial DNA evokes epithelial IL-8 production by a MAPK-dependent, NFκB-independent pathway

被引:139
作者
Akhtar, M [1 ]
Watson, JL [1 ]
Nazli, A [1 ]
McKay, DM [1 ]
机构
[1] McMaster Univ, Intestinal Dis Res Programme, Dept Pathol & Mol Med, Hamilton, ON L8N 3Z5, Canada
关键词
TLR-9; AP-1; signal; permeability; COX-2;
D O I
10.1096/fj.02-0950fje
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Recognition of bacterial products by the innate immune system is dependent on pattern-recognition receptors: toll-like receptor 9 (TLR-9) in the case of bacterial DNA. We hypothesized that bacterial DNA can directly affect enteric epithelial cells. RT-PCR revealed constitutive TLR-9 mRNA expression in three human colonic epithelial cell lines (T84, HT-29, Caco-2) and THP-1 monocytes. Epithelial cells, in six-well culture plates or on filter supports, were exposed to E. coli DNA (1-50 mug/ml), synthetic CpG-rich oligonucleotides, or calf thymus DNA for 6-48 h. Exposure to E. coli DNA resulted in an increase in IL-8 mRNA, and a time- and dose-dependent increase in IL-8 secretion. Also, CpG oligonucleotides induced epithelial IL-8 production, whereas calf thymus DNA did not. Exposure to E. coli DNA resulted in phosphorylation of ERK 1/2 MAPK and inhibitors of ERK activity (PD98059, UO126) significantly reduced the evoked IL-8 production. In contrast, inhibitors of NFkappaB activity (PDTC, SN50) did not block E. coli DNA-induced IL-8 production. Electrophoretic mobility shift assays revealed that E. coli DNA stimulated epithelial AP-1 but not NFkappaB activation. The barrier (i.e., transepithelial resistance) and ion transport parameters of epithelial monolayers (assessed in Ussing chambers) were unaltered following E. coli DNA exposure. Thus model gut epithelia express TLR-9 mRNA and, while maintaining their barrier function, can respond to E. coli DNA by increased IL-8 production.
引用
收藏
页码:1319 / +
页数:21
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